Networking :: Local Dns Server Cache Size Optimization

Does anybody have some thoughts about a local dns server cache size? What is the optimal one? In terms of memory consumption and number of re-enters into the cache. Lets say that default size is 150, so I've change this to 500 and after some time I see 379 re-enters into the cache. Simply put I need to increase the cache size 2 times. But due to the fact that browser preloads dns names it is not possible to interpret the number of overwrites in terms that it is not possible to say if useful cache entries were overwritten or those that the browser precached ( in other words not needed ). In this case it is ok to overwrite unwanted entries because it is not likely that I'll need these entries anyway

I'm running the dnsmasq on an embedded system with limited ram and with an umts dongle attached. It is important to keep the cache size as small as possible to reduce memory usage and at the same time to reduce number of external lookups because dns latency of the umts connection is high (1-2sec for the dns query)